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382 Multibody Systems Approach to Vehicle Dynamics
Fig. 6.51 Superimposed graphical animation of a double lane change
manoeuvre
To appreciate the use of computer simulations to represent this manoeuvre
an example of the superimposed animated wireframe graphical outputs for
this simulation is given in Figure 6.51.
In this study the influence of suspension modelling on the accuracy of the
simulation outputs is initially discussed based on results obtained using the
four vehicle models described in section 6.4 and summarized schematically
again here in Figure 6.52. The models shown can be thought of as a set of
models with evolving levels of elaboration leading to the final linkage model
that involves the modelling of the suspension linkages and the bushes.
For each of the vehicle models described here it is possible to estimate the
model size in terms of the degrees of freedom in the model and the number
of equations that MSC.ADAMS uses to formulate a solution. The calculation
of the number of degrees of freedom (DOF) in a system is based on the
Greubler equation given in Chapter 3. It is therefore possible for any of
the vehicle models to calculate the degrees of freedom in the model. An
example is provided here for the equivalent roll stiffness model where the
degrees of freedom can be calculated as follows:
Parts 9 6 54
Rev 8 5 40
Motion 2 1 2
Σ DOF 12
In physical terms it is more meaningful to describe these degrees of freedom
in relative terms as follows. The vehicle body part has 6 degrees of freedom.
The two axle parts each have 1 rotational degree of freedom relative to the